Planets form sequentially like falling dominos

Over 5,000 planetary systems have been identified so far, with more than 1,000 confirmed to host multiple planets. These planets originate in protoplanetary disks, dense clouds of gas and dust surrounding young stars. However, the detailed process of forming multi-planet systems, such as our Solar System, remains elusive.

One exceptional system under study is PDS 70, a young star located 367 light-years away in the constellation Centaurus. This is the only known system where fully formed planets have been confirmed within a protoplanetary disk via optical and infrared observations. Earlier research using the Atacama Large Millimeter/submillimeter Array (ALMA) identified a dust ring outside the orbits of two planets in this system but could not provide detailed insights into the dust's distribution.

A research team led by Kiyoaki Doi, now a postdoctoral fellow at the Max Planck Institute for Astronomy, utilized high-resolution ALMA observations at longer radio wavelengths to penetrate deeper into the dust cloud around PDS 70. The data revealed a distinct dust concentration in the ring's northwestern region, just outside the orbits of the existing planets. This suggests that interactions between the planets and the surrounding disk concentrate dust grains into specific areas. These clumps of dust likely grow into new planets.

The study provides strong observational evidence that planetary systems, including our Solar System, form through a sequential process. As planets form closer to the star, they shape the surrounding environment, encouraging the formation of additional planets farther out. This process unfolds like a chain reaction, with each planet setting the stage for the next, much like falling dominos.

Research Report:Asymmetric Dust Accumulation of the PDS 70 Disk Revealed by ALMA Band 3 Observations